CH717007A2 - Personal ornament and method of producing a personal ornament. - Google Patents

Abstract

The invention relates to a personal ornament, for example a watch trim element, in an alloy comprising, in percentage by mass: C: 0.10% or less; Si: 1.5% or less; Mn: 1.5% or less; P: 0.050% or less; S: 0.050% or less; O: 0.020% or less; Ni: 15.0 to 38.0%; Cr: 17.0 to 27.0%; Mo: 4.0-8.0%; Cu: 3.0% or less; N: 0.55% or less; And the remainder including iron and impurities. The invention also relates to methods of making such a personal ornament. The object of the invention is to provide a personal ornament with better corrosion resistance.

Description

BACKGROUND

1. Field of the invention

Embodiments of the present invention relate to a personal ornament and a method of producing a personal ornament.

2. Description of the prior art

Recently, as personal adornments to wear such as watches, necklaces, brooches and earrings, there are, for example, those using stainless steel as described in patent document 1 (JP-A-2019 -168407).

[0003] Furthermore, the demand for corrosion resistance in personal ornaments is growing more and more.

As a method of improving the corrosion resistance of a personal ornament, there is a method of producing a personal ornament with a material containing Cr and Mo in large amounts. On the other hand, when a personal ornament is produced with a material containing Cr and Mo in large amounts, in a cross section of the material containing Cr and Mo in large amounts, there remains a compound with high contents of Cr and Mo. The compound with high Cr and Mo contents has a different phase from the parent phase, and therefore, a problem exists that the specularity of the personal ornament is deteriorated. Further, the compound with high Cr and Mo contents decreases the Cr and Mo contents of the parent phase, and therefore a problem is that the corrosion resistance of the personal ornament is deteriorated.

SUMMARY OF THE INVENTION

Embodiments of the present invention have been made in order to solve the aforementioned problems, and aim to provide a personal ornament having excellent corrosion resistance, excellent specularity and a method of producing the ornament. staff.

[0006] More particularly, the present invention relates to: (1) A personal ornament in which chemical components include, in mass%: C: 0.10% or less; Si: 1.5% or less; Mn: 1.5% or less; P: 0.050% or less; S: 0.050% or less; O: 0.020% or less; Ni: 15.0 to 38.0%; Cr: 17.0 to 27.0%; Mo: 4.0-8.0%; Cu: 3.0% or less; and N: 0.55% or less, the remainder comprises Fe and impurities, a structure contains austenite at 95% or more in% of its area, when a diameter of a circle having the smallest possible area can include an intermetallic compound inside is defined as the size of the intermetallic compound, on an exposed surface of the personal ornament, the number of intermetallic compounds whose size is 150 µm or more is 0, and the number of intermetallic compounds whose size is 13 µm or more and less than 150 µm is 3 or less, an average diameter of an equivalent circle of the austenite is 150 µm or less, and a PRE defined by the following formula (1) is 40 or more: PRE = [Cr] + 3.3 [Mo] + 16 [N] ... (1) in which [Cr], [Mo] and [N] denote the contents in% by mass of Cr, Mo and N in a composition of components of the personal ornament, and 0 is substituted when such a component is not contained. (2) The personal ornament according to 1, wherein the chemical components further comprise, in mass%, one or two or more types selected from: Al: 0.001 to 0.10%; Co: 0.001 to 3.0%; W: 0.001 to 8.0%; Ta: 0.001 to 1.0%; Sn: 0.001 to 1.0%; Sb: 0.001 to 1.0%; Ga: 0.001 to 1.0%; Ti: 0.001 to 1.0%; V: 0.001 to 1.0%; Nb: 0.001 to 1.0%; Zr: 0.001 to 1.0%; Te: 0.001 to 1.0%; Se: 0.001 to 1.0%; B: 0.0001 to 0.01%; Ca: 0.0001 to 0.05%; Mg: 0.0001 to 0.05%; and a rare earth element: 0.001 to 1.0%. (3) The personal ornament according to 1 or 2, in which the personal ornament constitutes the exterior of a watch. (4) A method of producing the 1 to 3 personal ornament comprising: a step of producing a plate material; a heat treatment step of subjecting the plate material to heat treatment; and a cold rolling step of subjecting the plate material to plastic deformation work, wherein in the heat treatment step, a heat treatment temperature is 1350 to 1600 K, and a heat treatment time satisfies the following formula (2), and in the cold rolling step, a rolling reduction rate is 7-50% tdif≥ (6869 / Tdif- 4.3326) × λ <2> ... (2) where Tdif represents the heat treatment temperature (K), tdif represents the heat treatment time (hour), and λ represents a plate thickness ( mm) of the plate material. (5) A method of producing the personal ornament according to 1 comprising: a step of producing a bar material; a heat treatment step of subjecting the bar material to heat treatment; and a cold drawing step of subjecting the bar material to plastic deformation work, wherein in the heat treatment step, a heat treatment temperature is 1350 to 1600 K, and a heat treatment time satisfies the following formula (3), and in the cold drawing step, an area reduction rate is 7 to 50%: tdif≥ (6869 / Tdif- 4.3326) × d ... (3) where Tdif represents the heat treatment temperature (K), tdif represents the heat treatment time (hour), and d represents the diameter of an equivalent circle ( mm) to the bar material. (6) A method of producing the personal ornament according to 1 to 3, comprising: a step of producing a plate material or a bar material; a heat treatment step of subjecting the plate material or the bar material to heat treatment; a hot forging step of subjecting the plate material or the bar material to hot forging; and a cold forging step of subjecting the plate material or the bar material to cold forging, wherein in the heat treatment step, a heat treatment temperature is 1350 to 1600 K, in the case of the plate material, a heat treatment time satisfies the following formula (2), and in the case of the bar material, a heat treatment time satisfies the following formula (3): tdif≥ (6869 / Tdif- 4.3326) × λ <2> ... (2) tdif≥ (6869 / Tdif- 4.3326) × d ... (3) in which in formula (2), Tdif represents the heat treatment temperature (K), tdif represents the heat treatment time (hour), and λ represents a plate thickness (mm) of the plate material, and in formula (3), Tdi represents the heat treatment temperature (K), tdi represents the heat treatment time (hour), and d represents a diameter of an equivalent circle ( mm) of the bar material.

According to embodiments of the present invention, a personal ornament having excellent corrosion resistance and excellent specularity and a method of producing personal ornament can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an external view of a personal ornament according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0009] The present inventor has conducted various studies to improve the corrosion resistance and specularity of a personal ornament, and therefore, has obtained the following findings.

In a cross section of a commercially available material having a PRE of 40 or more, an intermetallic compound is present in a large amount. Here, the intermetallic compound is an intermetallic compound with higher Cr and Mo contents than the Cr and Mo contents of the parent phase.

When the material containing an intermetallic compound in a large amount and having a PRE of 40 or more is polished, the intermetallic compound appears as a heterogeneous phase, and a mirror face applicable to a personal ornament cannot be obtained. Further, the intermetallic compound lowers the Cr and Mo contents of the parent phase, and therefore, excellent corrosion resistance cannot be exhibited on an exposed side of the intermetallic compound.

The present invention has been carried out as a result of studies described above, and hereinafter, with respect to the embodiments according to the present invention, the reason for limiting the requirements of the technical characteristics and the preferred aspects will be described sequentially. First, a personal ornament according to an embodiment of the present invention will be described. The personal ornament described below is a timepiece trim element 100 as shown in Figure 1.

(Composition of personal ornamentation components)

The chemical components contained in the personal ornament according to an embodiment of the present invention (hereinafter sometimes abbreviated "personal ornament") and the reasons for limiting the contents of the respective components will be described. Note that in the following description, "%" means "% by mass" unless otherwise specified.

C: 0.10% or less

[0014] The content of C should be equal to 0.10% or less. When the C content exceeds 0.10%, Cr carbide is excessively formed, and the corrosion resistance of the personal ornament is deteriorated. The upper limit of the C content is preferably 0.08% or less, more preferably 0.05% or less. On the other hand, C is an element which forms austenite, and therefore it can be contained. The lower limit of the C content preferably 0.005% or more, more preferably 0.010% or more.

If: 1.5% or less

The Si content must be equal to 1.5% or less. When the Si content exceeds 1.5%, the deposition of an intermetallic compound is promoted, and the corrosion resistance and specularity of the personal ornament are deteriorated. The upper limit of the Si content is preferably 1.0% or less, more preferably 0.6% or less. On the other hand, Si is an element having a deoxidizing effect, and therefore it can be contained. The lower limit of the Si content is preferably 0.10% or more, more preferably 0.30% or more.

Mn: 1.5% or less

[0016] The Mn content should be equal to 1.5% or less. When the Mn content exceeds 1.5%, the corrosion resistance of the personal ornament is deteriorated. The upper limit of the Mn content is preferably 1.0% or less, more preferably 0.8% or less. On the other hand, Mn is an element which forms austenite and an element having a deoxidizing effect, and therefore it can be contained. The lower limit of the Mn content is preferably 0.01% or more, more preferably 0.10% or more.

P: 0.050% or less

The P content should almost be eliminated, that is to say reduced to 0.050% or less. When the P content exceeds 0.050%, the sturdiness of the personal ornament is deteriorated. The upper limit of the P content is preferably 0.045% or less, more preferably 0.035% or less.

S: 0.050% or less

The S content should be virtually eliminated, that is to say reduced to 0.050% or less. When the S content exceeds 0.050%, the strength and corrosion resistance of the personal ornament is deteriorated. The upper limit of the S content is preferably 0.040% or less, more preferably 0.015% or less.

O: 0.020% or less

The O content should be virtually eliminated, that is to say reduced to 0.020% or less. When the O content exceeds 0.020%, the sturdiness of the personal ornament is deteriorated. The upper limit of the O content is preferably 0.015% or less, more preferably 0.010% or less.

Ni: 15.0 to 38.0%

The Ni content should be set between 15.0 to 38.0%. When the Ni content is less than 15.0%, ferrite is excessively formed, and the strength and corrosion resistance of the personal ornament is deteriorated. The lower limit of the Ni content is preferably 17.0% or more, more preferably 18.0% or more. On the other hand, when the Ni content exceeds 38.0%, the effect of improving the corrosion resistance of the personal ornament is saturated. Besides, the content of Ni becomes excessively large, and the price of personal adornment becomes high. The upper limit of the Ni content is preferably 30.0% or less, more preferably 20.0% or less.

Cr: 17.0 to 27.0%

The Cr content should be set between 17.0 to 27.0%. When the Cr content is less than 17.0%, the corrosion resistance of the personal ornament is deteriorated. The lower limit of the Cr content is preferably 18.0% or more, more preferably 19.0% or more. On the other hand, when the Cr content exceeds 27.0%, ferrite and an intermetallic compound are formed in excess, and the strength and corrosion resistance of the personal ornament are deteriorated. The upper limit of the Cr content is preferably 25.0% or less, more preferably 21.0% or less.

MB: 4.0 to 8.0%

The Mo content should be set between 4.0 to 8.0%. When the Mo content is less than 4.0%, the corrosion resistance of the personal ornament is deteriorated. The lower limit of the Mo content is preferably 5.0% or more, more preferably 6.0% or more. On the other hand, when the Mo content exceeds 8.0%, excess ferrite and an intermetallic compound are formed, and the strength and corrosion resistance of the personal ornament are deteriorated. The upper limit of the Mo content is preferably 7.5% or less, more preferably 7.0% or less.

Cu: 3.0% or less

[0023] The Cu content should be 3.0% or less. When the Cu content exceeds 3.0%, cracking is likely to occur during casting. The upper limit of the Cu content is preferably 1.0% or less, more preferably 0.8% or less. On the other hand, Cu has the effect of suppressing the progression of corrosion when corrosion has taken place, and therefore it can be contained. The lower limit of the Cu content is preferably 0.01% or more, more preferably 0.10% or more.

N: 0.55% or less

[0024] The N content should be equal to 0.55% or less. When the N content exceeds 0.55%, cracking is likely to occur during casting. The upper limit of the N content is preferably 0.50% or less, more preferably 0.35% or less, still more preferably 0.25% or less. On the other hand, I'N has an effect of improving the corrosion resistance and an effect of forming austenite, and therefore it can be contained. The lower limit of the N content is preferably 0.05% or more, more preferably 0.10% or more, still more preferably 0.15% or more.

PRE is 40 or more.

A PRE predefined by the following formula (1) must be 40 or more. When the PRE is less than 40, the corrosion resistance of the personal ornament is deteriorated. PRE = [Cr] + 3.3 [Mo] + 16 [N] ... (1)

It should be noted that [Cr], [Mo] and [N] in formula (1) means the contents in% by mass of Cr, Mo and N in a composition of components of the personal ornament, and 0 is substituted when such a component is not contained.

The personal ornament according to this embodiment may further contain, in mass%, one or two or more types selected from among AI, Co, W, Ta, Sn, Sb, Ga, Ti, V, Nb , Zr, Te, Se, B, Ca, Mg and a rare earth element other than the aforementioned elements. It should be noted that these elements do not need to be contained, and therefore the lower limit of their content is 0.

Al: 0.10% or less

The personal ornament according to this embodiment can contain AI at 0.10% or less. AI is an element having a deoxidizing effect, and therefore it can be contained. The content thereof when AI is contained to achieve this effect is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Al content exceeds 0.10%, excess aluminum nitride or aluminum oxide is formed, and the corrosion resistance and sturdiness of the personal ornament are deteriorated. The upper limit of the AI content is preferably 0.05% or less, more preferably 0.02% or less.

Co: 3.0% or less

The personal ornament according to this embodiment can contain Co at 3.0% or less. Co forms austenite and has an effect of suppressing the formation of an intermetallic compound, and therefore it can be contained. The content thereof when Co is contained to achieve this effect is 0.001% or more, more preferably 0.1% or more. On the other hand, when the Co content exceeds 3.0%, the machinability is deteriorated. The upper limit of the Co content is preferably 2.0% or less, more preferably 1.5% or less.

W: 8.0% or less

[0031] The personal ornament according to this embodiment may contain W at 8.0% or less. W has an effect of improving the corrosion resistance, and therefore it can be contained. The content thereof when W is contained to achieve this effect is 0.001% or more, more preferably 0.1% or more. On the other hand, when the W content exceeds 8.0%, the machinability is deteriorated. The upper limit of the W content is preferably 5.0% or less, more preferably 1.0% or less.

Ta: 1.0% or less

[0032] The personal ornament according to this embodiment can contain Ta at 1.0% or less. Ta has the effect of refining crystal grains and improving corrosion resistance effect, and therefore it can be contained. The content thereof when Ta is contained to achieve these effects is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Ta content exceeds 1.0%, the usability is deteriorated. The upper limit of the Ta content is preferably 0.5% or less, more preferably 0.1% or less.

Sn: 1.0% or less

The personal ornament according to this embodiment can contain Sn at 1.0% or less. Sn has the effect of improving corrosion resistance, and therefore it can be contained. The content thereof when Sn is contained to achieve this effect is 0.001% or more, more preferably 0.005% or more. On the other hand, when the Sn content exceeds 1.0%, the usability is deteriorated. The upper limit of the Sn content is preferably 0.5% or less, more preferably 0.3% or less.

Sb: 1.0% or less

The personal ornament according to this embodiment can contain Sb at 1.0% or less. Sb has the effect of improving corrosion resistance, and therefore it can be contained. The content thereof when Sb is contained to achieve this effect is 0.001% or more, more preferably 0.005% or more. On the other hand, when the content of Sb exceeds 1.0%, the usability is deteriorated. The upper limit of the Sb content is preferably 0.5% or less, more preferably 0.3% or less.

Ga: 1.0% or less

[0035] The personal ornament according to this embodiment can contain Ga at 1.0% or less. Ga has an effect of improving corrosion resistance and an effect of improving ease of use, and therefore it can be contained. The content thereof when Ga is contained to achieve these effects is 0.001% or more, more preferably 0.015% or more. On the other hand, when the Ga content exceeds 1.0%, the effect of improving corrosion resistance and the effect of improving ease of use are saturated. The upper limit of the Ga content is preferably 0.5% or less, more preferably 0.3% or less.

Ti: 1.0% or less

The personal ornament according to this embodiment can contain Ti at 1.0% or less. Ti has the effect of improving the corrosion resistance by fixing C and N as a carbonitride and an effect of refining the crystal grains, and hence it can be contained. The content thereof when Ti is contained to achieve these effects is 0.001% or more, more preferably 0.01% or more. On the other hand, when the Ti content exceeds 1.0%, excessive amounts of an oxide and a nitride are formed, and the ease of use is deteriorated. The upper limit of the Ti content is preferably 0.5% or less, more preferably 0.3% or less.

V: 1.0% or less

[0037] The personal ornament according to this embodiment may contain V at 1.0% or less. The V has the effect of improving the corrosion resistance by fixing C and N as a carbonitride and an effect of refining the crystal grains, and hence it can be contained. The content thereof when V is contained to achieve these effects is 0.001% or more, more preferably 0.02% or more. On the other hand, when the V content exceeds 1.0%, excessive amounts of an oxide and nitride are formed, and the usability is deteriorated. The upper limit of the V content is preferably 0.9% or less, more preferably 0.5% or less.

Nb: 1.0% or less

The personal ornament according to this embodiment can contain Nb at 1.0% or less. The Nb has the effect of improving the corrosion resistance by fixing C and N as a carbonitride and an effect of refining the crystal grains, and hence it can be contained. The content thereof when Nb is contained to achieve these effects is 0.001% or more, more preferably 0.02% or more. On the other hand, when the Nb content exceeds 1.0%, excessive amounts of an oxide and nitride are formed, and the usability is deteriorated. The upper limit of the Nb content is preferably 0.5% or less, more preferably 0.2% or less.

Zr: 1.0% or less

The personal ornament according to this embodiment may contain Zr at 1.0% or less. Zr has the effect of improving the strength and an effect of refining the crystal grains, and therefore it can be contained. The content thereof when Zr is contained to achieve these effects is 0.001% or more, more preferably 0.02% or more. On the other hand, when the Zr content exceeds 1.0%, the usability is deteriorated. The upper limit of the Zr content is preferably 0.5% or less, more preferably 0.2% or less.

Te: 1.0% or less

The personal ornament according to this embodiment can contain Te at 1.0% or less. Te has the effect of improving machinability, and therefore it can be contained. The content thereof when Te is contained to achieve this effect is 0.001% or more, more preferably 0.01% or more. On the other hand, when the Te content exceeds 1.0%, the corrosion resistance is deteriorated. The upper limit of the Te content is preferably 0.05% or less, more preferably 0.02% or less.

Se: 1.0% or less

The personal ornament according to this embodiment may contain Se at 1.0% or less. Se has the effect of improving machinability, and therefore it can be contained. The content thereof when Se is contained to achieve this effect is 0.001% or more, more preferably 0.01% or more. On the other hand, when the Se content exceeds 1.0%, the corrosion resistance is deteriorated. The upper limit of the Se content is preferably 0.2% or less, more preferably 0.1% or less.

B: 0.01% or less

[0042] The personal ornament according to this embodiment may contain B at 0.01% or less. The B has the effect of improving ease of use when hot, and therefore it can be contained. The content thereof when B is contained to achieve this effect is 0.0001% or more, more preferably 0.0005% or more. On the other hand, when the B content exceeds 0.01%, the corrosion resistance is deteriorated. The upper limit of the B content is preferably 0.005% or less, more preferably 0.003% or less.

Ca: 0.05% or less

The personal ornament according to this embodiment can contain Ca at 0.05% or less. Ca has the effect of improving usability when hot, and therefore it can be contained. The content thereof when Ca is contained to achieve this effect is 0.0001% or more, more preferably 0.0005% or more. On the other hand, when the Ca content exceeds 0.05%, the ease of hot use is rather deteriorated. The upper limit of the Ca content is preferably 0.005% or less, more preferably 0.003% or less.

Mg: 0.05% or less

The personal ornament according to this embodiment can contain Mg at 0.05% or less. The Mg has the effect of improving the usability in hot, and therefore it can be contained. The content thereof when Mg is contained to achieve this effect is 0.0001% or more, more preferably 0.0005% or more. On the other hand, when the Mg content exceeds 0.05%, the ease of hot use is rather deteriorated. The upper limit of the Mg content is preferably 0.005% or less, more preferably 0.003% or less.

Rare earth element: 1.0% or less

The personal ornament according to this embodiment may contain a rare earth element at 1.0% or less. The rare earth element has the effect of improving the usability when hot, and therefore it can be contained. The content thereof when the rare earth element is contained to achieve this effect is 0.001% or more, more preferably 0.005% or more. On the other hand, when the rare earth element content exceeds 1.0%, the ease of use in hot conditions is rather deteriorated. The upper limit of the rare earth element content is preferably 0.1% or less, more preferably 0.03% or less.

Remainder including Fe and impurities

The remainder other than the elements described above includes Fe and impurities. Further, any element other than the respective elements described above can be contained without altering the effect of this embodiment. The remainder other than the elements described above is preferably composed of Fe and impurities.

A measurement method for the composition of the personal ornament compound is as follows. First, with respect to an element other than O and N, in the case of a plate material, a sample is taken from 1/4 of the thickness of the plate, and in the case of a bar material, a sample is taken from the 1/2 length of a line segment connecting the surface and the center. Hereinafter, the composition of the compound is measured according to JIS G 1256: 2013 (Iron and steel - Methods for X-ray fluorescence spectrometric analysis).

Further, O is measured for the aforementioned sample using JIS G 1239: 2014 (Infrared absorption method after fusion under inert gas). N is measured for the aforementioned sample using JIS G 1228: 2006 (Iron and steel - Methods for determination of nitrogen content).

The shape of the plate material is as described in JIS G 4304: 2012 (Hot-rolled stainless steel plate, sheet and strip) or JIS G 4305: 2012 (Cold-rolled stainless steel plate, sheet and strip) .

Further, the shape of the bar material is as described in JIS G 4303: 2012 (Stainless steel bars).

(Structure of personal ornament)

The reason for limiting the structure of the personal ornament according to an embodiment of the present invention will be described. It should be noted that in the following description, the percentage "%" means "percentage% in terms of area unless otherwise indicated.

Austenitis contained at 95% or more

The austenite should be contained at 95% or more. When the austenite is contained within 95%, the amount of intermetallic compound becomes excessively large, and the specularity and corrosion resistance of the personal ornament are deteriorated. The austenite is preferably contained at 97% or more, more preferably at 98% or more, still more preferably at 99% or more.

When a heat treatment of the present invention is carried out, a crystalline defect observed during a usual annealing treatment is recovered or a characteristic structure occurs other than the formation of a double annealing. For example, a predominantly recrystallized austenite crystal grain is observed which corrodes an old austenite crystal grain including a twin. In addition, depending on the conditions of the heat treatment, sometimes a coarse grain of austenite crystal recrystallized secondarily is also observed. Such a structure can be confirmed using an electron backscatter diffraction (EBSD) device attached to an electron microscope.

A measurement method for a% area of the austenite is as follows. First, it is performed using a scanning electron microscope - backscattered electron image (SEM-BSE). As for the magnification of the measurement, the measurement is performed with a magnification so that a square of about 710 µm side is included in the field of view, which is the same as a standard diagram described in JIS G 0555, Microscopic testing method for the non-metallic inclusions in steel (2003).

As for the place of measurement, in the case of a plate material, the observation is carried out at a position where a part at the center of the thickness of the plate is parallel to one side (approximately 710 μm ) of the square of the visual field and passes through the center of the square. In the case of a bar material, the observation is made at a position where the center of the cross section perpendicular to the longitudinal direction becomes the center of the square field of view. In the plate material and the bar material, an intermetallic compound with high contents of Cr and Mo is present in greater quantity at the above-mentioned observation sites. On the exposed surface of the personal ornament, the austenite surface fraction is higher and the intermetallic compound surface fraction is lower at the aforementioned observation sites.

In the backscattered electronic image, compared to the contrast of the parent phase which is austenite, the intermetallic compound with high Cr and Mo contents looks bright (white), and a non- inclusion. metallic looks dark (black). When a captured image is displayed, the measurement site is adjusted so that a part where compounds other than austenite collect is located in the center of the aforementioned square.

Subsequently, a captured backscattered electronic image photograph is subjected to image analysis and is classified into three brightness pixel steps: an intermetallic compound (high brightness pixel), austenite (high brightness pixel). intermediate brightness), and a non-intermetallic compound (low-light pixel). The percentage of the number of pixels of the austenite to the total number of pixels is determined to be the% of the area of the austenite.

On the exposed surface of the personal ornament, the number of intermetallic compounds whose size is 150 µm or more is 0, and the number of intermetallic compounds whose size is 13 µm or more and less than 150 µm is 3 or less.

In the personal ornament according to this embodiment, on the exposed surface of the personal ornament, the number of intermetallic compounds whose size is 150 µm or more should be 0. When the number of intermetallic compounds including the size is 150 µm or more exceeds 0, the specularity and corrosion resistance of the personal ornament deteriorated. The size of the intermetallic compound is the diameter of a circle having the smallest area capable of including an intermetallic compound therein. The phrase “on the exposed surface of the personal ornament” refers to the surface of the personal ornament whose appearance can be observed.

[0060] Further, in the personal ornament according to this embodiment, on the exposed surface of the personal ornament, the number of intermetallic compounds whose size is 13 µm or more and less than 150 µm should be 3 or less. When the number of intermetallic compounds whose size is 13 µm or more and less than 150 µm exceeds 3, the specularity and corrosion resistance of the personal ornament are deteriorated.

The intermetallic compound has a different phase from the austenite which has the parent phase, and therefore the intermetallic compound and austenite have different appearances. Due to this, when the number of intermetallic compounds is excessively large, sufficient specularity applicable to personal ornament cannot be obtained.

Further, an area where the Cr and Mo contents are excessively small is formed on the side of the parent phase at the interface between the intermetallic compound and the austenite which has the parent phase. Therefore, when the number of intermetallic compounds is excessively large, the corrosion resistance of the personal ornament is deteriorated.

A measurement method for the number of intermetallic compounds whose size is 150 µm or more and intermetallic compounds whose size is 13 µm or more and less than 150 µm is as follows. First, using an optical microscope, a photograph of a structure of the exposed surface of the personal ornament is captured with 10 times magnification. In the captured photograph, the size of the intermetallic compound is measured. The size of the intermetallic compound is the diameter of a circle having the smallest area that can include an intermetallic compound inside. Then, the number of intermetallic compounds whose size is 150 µm or more and intermetallic compounds whose size is 13 µm or more and less than 150 µm is counted.

The average diameter of an equivalent circle of the austenite is 150 μm or less. The average diameter of an equivalent circle of the austenite should be 150 µm or less.

The average diameter of an equivalent circle of the austenite should be 150 μm or less. When the average diameter of an equivalent circle of austenite exceeds 150 µm, the specularity of the personal ornament is deteriorated. The average diameter of an equivalent circle of the austenite is preferably 70 µm or less.

A measurement method for the average diameter of an equivalent circle of austenite is as follows. The azimuth of an individual crystal grain is determined using an electron backscatter diffraction apparatus (EBSD apparatus) attached to an emission type SEM field. A place where an azimuth difference between adjacent pixels is 5 ° or more is defined as a crystal grain boundary. Further, the actual area of a crystal grain is measured, and the average diameter of an equivalent circle of austenite is calculated from the formula for determining the area of a circle. It should be noted that a treatment is performed in which an annealing twin is present in a crystal grain is not considered to determine the maximum grain size.

Remainder other than the intermetallic compound and austenite

The remainder other than the intermetallic compound and the austenite can include non-metallic phases such as an inclusion, an oxide, a nitride, and a carbide.

[0068] Examples of personal adornment according to this embodiment include, but are not limited to, a watch dressing element, a necklace, and eyeglasses. Here, examples of exterior watch elements include, but are not limited to, a case and a bracelet for a timepiece, and a case and a bracelet for a portable instrument having a function of a timepiece. watchmaking.

Next, a method of producing a personal ornament according to an embodiment of the present invention will be described. It should be noted that since the production method is different between a case where a plate material is used and a case where a bar material is used, and therefore, the case where a plate material is used and the case where bar material is used will be described separately.

[0070] The method of producing a personal ornament according to an embodiment of the present invention comprises a step of producing a plate material having the above-mentioned chemical components, a heat treatment step for subjecting the plate material to heat treatment, and a cold rolling step of subjecting the plate material to plastic deformation work.

(Plate material production step)

At the stage of producing a plate material, a known method can be used. At the stage of producing a plate material, although not particularly limited, for example, a method as described below can be adopted. In a melting furnace such as an electric furnace capable of applying pressure or a high frequency induction furnace capable of applying pressure, an alloy having the above-mentioned chemical composition is melted and cast into a steel ingot. Subsequently, the obtained steel ingot is hot worked to form a plate material having a desired shape. Then, after hot working, solid solution heat treatment is carried out.

(Heat treatment step)

In the heat treatment step, a heat treatment temperature should be 1350 to 1600 K. When the heat treatment temperature is less than 1350 K, the corrosion resistance and the specularity of the personal ornament are deteriorated. The heat treatment temperature is preferably 1473 K or more. On the other hand, when the heat treatment temperature exceeds 1600K, high temperature deformation due to its own weight of the material or partial melting occurs. The heat treatment temperature is preferably 1548 K or less.

In the heat treatment step, a heat treatment time must satisfy the following formula (2). tdif≥ (6869 / Tdif- 4.3326) × λ <2> ... (2)

[0074] It should be noted that in formula (2), Tdi represents the heat treatment temperature (K), tdi represents the heat treatment time (hour), and λ represents a plate thickness (mm) of the plate material. When the heat treatment time does not satisfy the formula (2), the amount of the intermetallic compound becomes excessively large, and the corrosion resistance and specularity of the personal ornament are deteriorated.

A heat treatment method can be by heating in an inert gas at an ambient temperature below atmospheric pressure. By heating in an inert ambient gas, sublimation of Cr during heat treatment is suppressed, and the corrosion resistance of the personal ornament is further improved.

After the heat treatment step, cooling to 60 ° C / min or more can be performed. By performing cooling to 60 ° C / min or more, re-deposition of the intermetallic compound or an increase in the content thereof is further suppressed, and the corrosion resistance and specularity of the personal ornament are further improved.

(Cold rolling stage)

At the cold rolling step, a rolling reduction rate should be 7 to 50%. When the rolling reduction rate is less than 7%, the average diameter of an equivalent circle of the austenite becomes excessively large, and the specularity of the personal ornament is deteriorated. The rolling reduction rate is preferably 13% or more. On the other hand, when the rolling reduction rate exceeds 50%, the hardness of the material becomes excessively large. As a result, the machinability or pressability of the material is deteriorated.

(Hot forging step and cold forging step)

The method of producing a personal ornament according to one embodiment of the present invention may include a hot forging step to achieve hot plastic deformation by heating the plate material to a temperature in a range where l The austenite is stable and a cold forging step to achieve cold plastic deformation by omitting the aforementioned cold rolling step. The amount of plastic deformation in the hot forging step and the cold forging step is not particularly limited as long as the average diameter of an equivalent circle of the austenite on the exposed surface of the personal ornament is 150 µm or less. The amount of plastic deformation in the hot forging step and the cold forging step is preferably selected such that the average diameter of an equivalent circle of the austenite on the exposed surface of the personal ornament is 70 µm or less. The hot forging step and the cold forging step tend to increase the yield of the material over the cold rolling step. Therefore, it is preferable to perform the hot forging step and the cold forging step by omitting the cold rolling step.

Next, a method of producing a personal ornament according to another embodiment of the present invention will be described.

[0080] The method of producing a personal ornament according to another embodiment of the present invention includes a step of producing a bar material having a chemical composition described in the above-mentioned embodiment, a step of heat treatment. subjecting the bar material to heat treatment, and a cold drawing step subjecting the bar material to plastic deformation work.

(Production step of a bar material)

At the stage of producing a bar material, a known method can be used.

(Heat treatment step)

In the heat treatment step, a heat treatment temperature should be 1350 to 1600 K. When the heat treatment temperature is less than 1350 K, the amount of intermetallic compound becomes excessively large, and the resistance to corrosion and specularity of personal ornament deteriorated. The heat treatment temperature is preferably 1473 K or more. On the other hand, when the heat treatment temperature exceeds 1600K, high temperature deformation due to its own weight of the material or partial melting occurs. The heat treatment temperature is preferably 1548 K or less.

In the heat treatment step, a heat treatment time must satisfy the following formula (3). tdif≥ (6869 / Tdif- 4.3326) × d ... (3)

It should be noted that in formula (3), Tdifrepresents the heat treatment temperature (K), tdifrepresents the heat treatment time (hour), and d represents the diameter of an equivalent circle (mm) of the material in bar. When the heat treatment time does not satisfy the formula (3), the amount of the intermetallic compound becomes excessively large, and the corrosion resistance and specularity of the personal ornament are deteriorated.

The diffusion of the concentration of Cr or Mo during the heat treatment of the intermetallic compound with high contents of Cr and Mo goes unidimensionally to both sides in the direction of rolling from the central plane in the direction of thickness in the plate material, and advances circumferentially from the central axis simultaneously in two dimensions in the direction of drawing the wire of the bar material.

In formula (2) relative to the heat treatment time for the plate material, a time is assumed during which the amount of diffusion of the intermetallic compound with high Cr and Mo contents towards the austenite in periphery becomes equivalent in the plate material and in the bar material. Then, in the bar material used for personal adornment, formula (3) is derived by substituting plate thickness λ <2> for diameter d.

While the conditions other than the heat treatment temperature and the heat treatment time, the conditions described in the method of producing a personal ornament according to the above-mentioned embodiment can be adopted.

(Cold drawing step)

In the cold drawing step, a reduction rate of the surface should be 7 to 50%. When the reduction rate of the area is less than 7%, the average diameter of an equivalent circle of the austenite becomes excessively large, and the specularity of the personal ornament is deteriorated. The reduction rate of the area is preferably 13% or more. On the other hand, when the reduction rate of the area exceeds 50%, the hardness of the material becomes excessively large. As a result, the machinability or ease of stamping of the material is deteriorated.

As the conditions other than the reduction rate of the area, the conditions described in the method of producing a personal ornament according to the above-mentioned embodiment can be adopted.

(Hot forging step and cold forging step)

[0090] The method of producing a personal ornament according to another embodiment of the present invention may include a hot forging step to achieve hot plastic deformation by heating the bar material to a temperature in a range where the austenite is stable and a cold forging step to achieve cold plastic deformation by omitting the aforementioned cold drawing step. The amount of plastic deformation in the hot forging step and the cold forging step is not particularly limited as long as the average diameter of an equivalent circle of the austenite on the exposed surface of the personal ornament is 150 µm or less. The amount of plastic deformation in the hot forging step and the cold forging step is preferably selected such that the average diameter of an equivalent circle of the austenite on the exposed surface of the personal ornament is 70 µm or less. The hot forging step and the cold forging step increase the yield of the material compared to the cold drawing step. Therefore, it is preferable to perform the hot forging step and the cold forging step by omitting the cold drawing step.

The method of producing a personal ornament according to the embodiment of the present invention described above may include a production step for making the personal ornament to have a predetermined shape and appearance. In the production step for making the personal ornament to have a predetermined shape and appearance, a known production method can be used.

Although not particularly limited, as an example, a method of producing an outer watch member will be shown. First, a method of producing a timepiece case from the exterior watch parts will be described.

(Production method of a timepiece case)

From a plate material or a bar material (hereinafter sometimes referred to a "material") subjected to the heat treatment step and to the cold rolling step or to In the cold drawing step described above, a blank is punched using a crank press and a punch die. The cut blank is molded into a near net shape using a plurality of molding dies. When the material is hardened by the work in the middle of the processing, an annealing step in which heating to a solution temperature or higher is carried out, followed by quenching in a bright annealing furnace is suitably carried out. .

In addition to the above description, a method of producing a blank adopting the hot forging step and the cold forging step will be described. First, the plate material or the bar material subjected to the aforementioned heat treatment step is molded into a shape close to the aforementioned perforated blank by hot forging using a press and a plurality of heat-resistant dies by. high frequency induction heating or heating in a heating furnace. After an oxide film on the surface is removed by pickling or sandblasting, a nearly clean-shaped blank is produced by cold working using a press and molding die. Process annealing can be carried out as appropriate in the middle of the hot forging step and the cold forging step.

It is preferred to improve the number of dies in the cold forging step by reducing the number of dies in the hot forging step. According to this, the average diameter of an equivalent circle of the austenite can be further decreased.

The pressed blank is subjected to several cutting and drilling steps, such as grinding the inside diameter, in order to serve as a reference for machining with a numerically controlled (CNC) lathe, a surface cutting for a press face, opening a tie hole for attaching a band or adjusting rod hole, and processing screws to secure a case back, thereby forming a case of unpolished timepiece.

The case of the unpolished timepiece is subjected to coarse polishing using a SALLAZ polisher equipped with waterproof abrasive papers # 360, # 800, # 1200 and # 2000. Subsequently, the waterproof sandpaper is replaced by an abrasive cloth, and the finish polishing is carried out using alumina abrasives with a grain size of 3 µm, 1 µm, 0.3 µm and 0.05 µm.

After the finish polishing, a gloss polishing is performed. Depending on the design of the exterior of the watch, decoration such as grooving using a rotating wire brush, or lapping treatment (sandblasting) by applying a mask may be performed. Brazing or gluing of an adjusting rod tube for fixing a crown is carried out, which makes it possible to complete a case. A case back or a bezel is also formed by the same process.

Subsequently, a method of producing a metal band from the outer watch elements will be described.

(Method of producing a metal strip)

[0100] From a material subjected to the heat treatment step and to the cold rolling step or the cold drawing step described above, a block is punched using a press in the same manner as the timepiece case, and the block is molded into a shape similar to a completed body using a molding press. In addition, surface cutting, drilling a pin hole for connecting blocks and polishing are performed. Finally, the blocks are connected in a predetermined order using a C-ring pin or the like, and a clasp to be used for attachment and detachment is attached.

[0101] It should be noted that the method of producing an outer watch element is not limited to the methods described above, and any known production method to be carried out in the production of an outer watch element. watch can be adopted.

[Examples]

[0102] Next, examples of the present invention will be described. The conditions shown in the examples are an example adopted to confirm the feasibility and effects of the present invention. Therefore, the present invention is not limited to this example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the spirit of the present invention.

(Heat treatment conditions)

[0103] Types of steel A to D having the component composition shown in Table 1 were prepared. A type of steel A having a plate thickness of 6 mm to 22 mm was subjected to heat treatment under the conditions shown in Table 2, and the material was quenched after the heat treatment. With respect to the material after the heat treatment, the number of intermetallic compounds whose size of the intermetallic compound is 150 µm or more, and intermetallic compounds in which its size is 13 µm or more and less than 150 µm was measured.

[0104] A measurement method for the compound composition of the material was as follows. As to an item other than N, first, a sample was collected from a 1/4 of the plate thickness portion of the plate material. Hereinafter, the composition of the compound was measured according to JIS G 1256: 2013 (Iron and steel - Methods for X-ray fluorescence spectrometric analysis).

N was measured for the sample using JIS G 1228: 2006 (Iron and steel - Methods for determination of nitrogen content).

[0106] A measurement method for the number of intermetallic compounds whose size is 150 µm or more, and intermetallic compounds whose size is 13 µm or more and less than 150 µm was as follows. First, using an optical microscope, a photograph of a structure of a central portion of the plate thickness was taken with 10 times magnification. In the photograph taken, the size of the intermetallic compound was measured. The size of the intermetallic compound is a diameter of a circle having the smallest area capable of including an intermetallic compound therein. Then, the number of intermetallic compounds whose size is 150 µm or more, and intermetallic compounds whose size is 13 µm or more and less than 150 µm was counted. In the plate material, the intermetallic compound with a high Cr and Mo content is present in the greatest amount in the central portion of the plate thickness. Therefore, the number of intermetallic compounds measured by the above-mentioned method is assumed to be the number of intermetallic compounds whose size is 150 µm or more, and the size is 13 µm or more and less than 150 µm. Further, the cold rolling step is carried out at room temperature, and therefore, the number of intermetallic compounds in the material does not change significantly.

[0107] With respect to intermetallic compounds whose size is 150 μm or more, when its number was 1, the measurement is terminated. Compared with intermetallic compounds whose size is 13 µm or more and less than 150 µm, when its number was 4, the measurement is completed. The results of measurements of the number of intermetallic compounds whose size is 13 µm or more and less than 150 µm are shown in Table 2. It should be noted that in Table 2, in all materials in which the number of compounds intermetallic compounds whose size is 13 µm or more and less than 150 µm was 0, the number of intermetallic compounds whose size is 150 µm or more was also 0.

[0108] The measurement method for the% area of austenite was as follows. First, it was performed using a scanning electron microscope - backscattered electron image (SEM-BSE). As for the magnification of the measurement, the measurement was performed with a magnification so that a square of about 710 µm on a side was included in the field of view, which is the same as a standard diagram described in JIS G 0555, Microscopic testing method for the non-metallic inclusions in steel (2003).

[0109] The location of the measurement was located at a position where the central portion of the plate thickness is parallel to one side (about 710 µm) of the square of the visual field and passes through the center of the square.

[0110] Subsequently, a captured backscattered electronic image photograph was subjected to image analysis and classified into three brightness pixel stages: intermetallic compound (high brightness pixel), austenite (high brightness pixel). intermediate brightness), and an intermetallic non-compound (low-light pixel). The percentage of the number of pixels of the austenite to the total number of pixels was determined to be a% of the area of the austenite. Further, the cold rolling step is carried out at room temperature, and therefore, the% of the area of the austenite in the material does not change significantly. Therefore, the% of the area of the austenite in the material after the heat treatment step was assumed to be the% of the area of the austenite of the personal ornament. The results of the% austenite surface measurements are shown in Table 3.

Table 1

[0111] A 0.015 0.50 0.95 0.020 0.004 18.0 20.2 6.2 0.022 41 B 0.015 0.50 0.95 0.020 0.004 18.0 21.0 6.2 0.022 42 C 0.02 0.06 0.60 0.020 0.004 16.0 22.0 4.5 0.058 38 D 0.02 0.06 1.00 0.020 0.004 10.5 16.0 2.2 - 23

Table 2

[0112] Plate thickness (mm) 1 10 40 2 4 8 10 12 18 1 10 40 6 4 or more 4 or more 0 4 or more 4 or more 0 0 0 0 4 or more 0 0 8 - 4 or more 0 0 - 4 or more 0 0 0 0 4 or more 0 0 10 - 4 or more 0 - - 4 or more 4 or more 4 or more 0 - 4 or more 0 12 - - 4 or more - - - - - 4 or more - - 0 22 - - 4 or more - - - - - 4 or more - - 4 or more

Table 3

[0113] Plate thickness (mm) 40 8 10 12 18 10 40 6 95 or more 95 or more 95 or more 95 or more 95 or more 95 or more 95 or more 8 95 or more 95 or more 95 or more 95 or more 95 or more 95 or more 95 or more 10 95 or more - - - 95 or more - 95 or more 12 - - - - - - 95 or more 22 - - - - - - -

As shown in Tables 2 and 3, when the conditions of the heat treatment in the heat treatment step satisfy the following formula (2), the% of the area of the austenite and the number of intermetallic compounds of which the size is 150 µm or more, and intermetallic compounds whose size is 13 µm or more and less than 150 µm were within the range of the present invention. The% of the austenite area was 95% or more under all conditions. In addition, the remainder of the structure was a non-metallic phase. tdif≥ (6869 / Tdif- 4.3326) × λ <2> ... (2)

[0115] It should be noted that in formula (2), Tdi represents the heat treatment temperature (K), tdi represents the heat treatment time (hour), and λ represents a plate thickness (mm) of the plate material.

(Cold rolling conditions)

[0116] A type A steel plate material having a thickness of 6 mm was subjected to a heat treatment at 1473 K for 12 hours. After the heat treatment, cold rolling was carried out to a predetermined thickness using a two-stage rolling mill. An amount of gradual reduction per pass was set at 0.10 mm, and the rolling was terminated after obtaining the predetermined thickness. The rolling reduction rate in cold rolling is shown in Table 4.

The rolled material was cut in a plane perpendicular to the direction of rolling. Relative to the cut material, a blank is punched using a crank press and a punch die. The cut blank is molded into a near net shape using a plurality of molding dies.

[0118] The pressed blank was subjected to grinding for the internal diameter in order to serve as a reference for the treatment with a numerically controlled (NC) lathe, a surface cut for a press face, an opening of a pointed hole or an oblong hole for fixing a bracelet, a making a thread for fixing a back, and a plurality of cutting and drilling steps, making it possible to obtain a non-case timepiece polish.

[0119] The unpolished timepiece case was subjected to coarse polishing using a SALLAZ polisher equipped with # 360, # 800, # 1200 and # 2000 waterproof abrasive papers. Subsequently, the waterproof abrasive paper was replaced by an abrasive cloth, and the finishing polishing was carried out using alumina abrasives with a grain size of 3 µm, 1 µm, 0.3 µm and 0.05 µm . After the finish polishing, a gloss polishing was performed.

[0120] Consequently, the timepiece cases of Examples 1 to 6 and Comparative Examples 1 to 4 were obtained. The hardness of the material immediately after cold rolling was measured. In the hardness measurements, a Vickers hardness meter was used. A load in the measurement of hardness was set at 0.3 kgf, and the retention time was set at 15 seconds. The results of the measurements obtained using the Vickers durometer are shown in Table 4.

The average diameter of an equivalent circle of grains of austenite crystals was determined as follows. An azimuth of an individual crystal grain was determined using an electron backscatter diffraction apparatus (EBSD apparatus) attached to an emission type SEM field. A place where an azimuth difference between adjacent pixels is 5 ° or more has been defined as a crystal grain boundary. Further, the actual area of a crystal grain was measured, and the average diameter of an equivalent circle of austenite was calculated from the formula for determining the area of a circle. It should be noted that a treatment is performed in which an annealing twin / double present in a crystal grain is not used to determine the maximum grain size. The results of the measurements of the mean diameter of an equivalent circle of austenite are shown in Table 4.

[0122] Compared to timepiece cases, specularity was measured by performing the appearance determination. Specularity was assessed in three grades: poor, average and good. The results of the specularity measurements are shown in Table 4.

Table 4

[0123] Example 1 7.0 210 medium 149 Example 2 9.9 230 medium 124 Example 3 12.5 235 medium 107 Example 4 15.2 247 good 70 Example 5 21.1 283 good 62 Example 6 31.5 309 good - Comparative example 1 0 176 poor 217 Comparative example 2 2.3 185 poor 203 Comparative example 3 5.0 202 poor 165 Comparative example 4 51.1 364 poor -

[0124] In Examples 1 to 6, the conditions of the heat treatment in the heat treatment step and the reduction rate of the rolling in the cold rolling were within the range of the present invention, and therefore the material. has not been excessively hardened. Therefore, the material had sufficient ease of use even after the cold rolling step. Further, the average diameter of an equivalent circle of the austenite does not become excessively large, and therefore, timepiece cases have sufficient specularity.

[0125] On the other hand, in Comparative Examples 1 to 3, the rate of reduction of rolling in cold rolling was insufficient, and therefore, the specularity of timepiece cases was insufficient. Further, in Comparative Example 4, the rolling reduction rate in the cold rolling was excessively high, and therefore, the usability of the material after the cold rolling step was insufficient.

(Corrosion resistance)

In Example 7, a part for a corrosion resistance test was prepared as follows. A type B steel plate material having a thickness of 2 mm was subjected to heat treatment at 1473 K for a period of 1.5 hours. After the heat treatment, the plate material was quenched. Subsequently, the plate material was subjected to cold rolling at a rolling reduction rate of 25%. The thickness of the plate material after cold rolling was 1.5mm. The plate material after cold rolling was cut into a rectangular shape with a height of 20 mm and a width of 40 mm. The corners were chamfered, and subsequently the rolled faces (two faces) and cut side faces (four faces) were mirror finished by performing the same polishing step as in the method of producing a casing. timepiece in example 1.

[0127] In Comparative Examples 5 to 7, heat treatment and cold rolling were not carried out. Parts for a corrosion resistance test were prepared in the same manner as in Example 7 except for this.

The corrosion resistance test was carried out as follows. Regarding the 10 sheets of rectangular pieces with mirror finish, a half-immersion test in saturated saline solution at 60 ° C was carried out. Specifically, a saturated saline solution in a state of coexistence with solid sodium chloride was placed in a container, and the workpiece was placed on a polytetrafluoroethylene stand capable of being tilted at an inclination of 30 ° from a direction. vertical, and poured into the container. Subsequently, the amount of liquid was adjusted so that the workpiece was in a state where it was dipped to a height of 10 mm in the sodium chloride solution. The vessel was left to stand in a temperature controlled bath at 60 ° C. The part was periodically removed, and after washing, the state of appearance of pitting or intergranular corrosion was confirmed using a stereoscopic microscope. The half-immersion test was carried out for 1000 hours at the longest time. The average time until the onset of corrosion in the sheets of the parts was determined to be the corrosion time. It should be noted that the corrosion time of the part which was not corroded up to 1000 hours was determined to be 1000 hours. The results of the corrosion resistance test are shown in Table 5.

Table 5

[0129] Example 7 B 42 808 or more Comparative example 5 B 42 768 or more Comparative example 6 C 38 275 Comparative example 7 D 23 23

[0130] In Example 7, the heat treatment and PRE conditions were within the scope of the present invention, and therefore, favorable corrosion resistance was demonstrated.

[0131] In Comparative Example 5, the heat treatment conditions were outside the range of the present invention, and therefore, the corrosion resistance was lower than in Example 7. In Comparative Example 6 and Comparative Example 7, the conditions of heat treatment and PRE were outside the range of the present invention, and therefore, the corrosion resistance was insufficient.

(Realization of cold forging step and hot forging step)

[0132] A test was also carried out when the hot forging step and the cold forging step are performed by omitting the cold rolling step and the cold drawing step.

[0133] In Example 8, a round bar of type A steel having an average diameter of a circle of 25 mm was used. The round bar was heat treated at 1523 K for 8 hours in an argon atmosphere. After the heat treatment, the round bar was quenched with nitrogen gas under pressure. The heat treated round bar was cut to a length of about 40mm, thereby forming a billet. The billet was hot forged to a shape close to that of a blank by heating it to 1473 K using a high frequency induction heating method and punching the billet using a plurality of heat resistant forging dies. After hot forging, an oxide film on the surface was removed by sandblasting or pickling, and then, cold forging was performed. Subsequently, a timepiece case was obtained by the same steps as in Examples 1 to 7.

[0134] In Example 9, a plate material of a type A steel having a plate thickness of 14 mm and a width of 40 mm was used. The conditions of the heat treatment of Example 9 were set at a heat treatment at 1523 K for a period of 36 hours. The plate material subjected to the heat treatment was cut to a length of about 35 mm. Subsequently, a timepiece case was obtained under the same conditions as in Example 8.

[0135] The equivalent mean circle diameters of the austenite and the specularity of Examples 8 and 9 were measured in the same way as in Examples 1 to 7. Therefore, the equivalent mean circle diameters of austenite Examples 8 and 9 are both 150 µm or less, and the specularity was also sufficient.

[0136] Therefore, according to the present invention, a personal ornament having both excellent corrosion resistance and specularity, as well as a method of producing the personal ornament can be provided, and the value of use in the same. industry is high.

Claims (6)

1. A personal ornament in which of the chemical components include, in% by mass: C: 0.10% or less; Si: 1.5% or less; Mn: 1.5% or less; P: 0.050% or less; S: 0.050% or less; O: 0.020% or less; Ni: 15.0 to 38.0%; Cr: 17.0 to 27.0%; Mo: 4.0-8.0%; Cu: 3.0% or less; and N: 0.55% or less, the remainder includes iron Fe and impurities, a structure contains austenite at 95% or more in% of area, when a diameter of a circle having the smallest area capable of including therein an intermetallic compound is defined as the size of the intermetallic compound, on an exposed area of the personal ornament, the number of intermetallic compounds whose size is 150 µm or more is 0, and the number of intermetallic compounds whose size is 13 µm or more and less than 150 µm is 3 or less, an average diameter of an equivalent circle of the austenite is 150 µm or less, and a PRE defined by the following formula (1) is 40 or more: PRE = [Cr] + 3.3 [Mo] + 16 [N] ... (1) wherein [Cr], [Mo] and [N] denote the mass% contents of Cr, Mo and N in a composition of components of the personal ornament, and 0 is substituted when such component is not contained . 2. The personal ornament according to claim 1, the chemical components further comprising, in mass%, one or two or more types selected below: Al: 0.001 to 0.10%; Co: 0.001 to 3.0%; W: 0.001 to 8.0%; Ta: 0.001 to 1.0%; Sn: 0.001 to 1.0%; Sb: 0.001 to 1.0%; Ga: 0.001 to 1.0%; Ti: 0.001 to 1.0%; V: 0.001 to 1.0%; Nb: 0.001 to 1.0%; Zr: 0.001 to 1.0%; Te: 0.001 to 1.0%; Se: 0.001 to 1.0%; B: 0.0001 to 0.01%; Ca: 0.0001 to 0.05%; Mg: 0.0001 to 0.05%; and a rare earth element: 0.001 to 1.0%. 3. The personal ornament according to claim 1 or 2, wherein the personal ornament is a watch dressing element. 4. A method of producing the personal ornament according to claim 1 comprising: a step of producing a plate material; a heat treatment step of subjecting the plate material to a heat treatment; and a cold rolling step consisting in subjecting the material of the plate to plastic deformation work, in which in the heat treatment step, a heat treatment temperature is 1350 to 1600 K, and a heat treatment time satisfies the following formula (2), and in the cold rolling step, a rolling reduction rate is 7 to 50%: tdif≥ (6869 / Tdif- 4.3326) × λ <2> ... (2) where Tdif represents the heat treatment temperature (K), tdif represents the heat treatment time (hour), and λ represents a plate thickness (mm) of the plate material. 5. A method of producing the personal ornament according to claim 1 comprising: a step of producing a bar material; a heat treatment step of subjecting the bar material to a heat treatment; and a cold drawing step of subjecting the bar material to plastic deformation work, in which in the heat treatment step, a heat treatment temperature is 1350 to 1600 K, and a heat treatment time satisfies the following formula (3), and in the cold drawing step, an area reduction rate is 7 to 50%: tdif≥ (6869 / Tdif- 4.3326) × d ... (3) where Tdif represents the heat treatment temperature (K), tdif represents the heat treatment time (hour), and d represents an equivalent circle diameter (mm) of the bar material. A method of producing the personal ornament according to claim 1, comprising: a step of producing a plate material or a bar material; a heat treatment step of subjecting the plate material or the bar material to a heat treatment; a hot forging step of subjecting the plate material or the bar material to hot forging; and a cold forging step of subjecting the plate material or the bar material to cold forging, in which in the heat treatment step, a heat treatment temperature is 1350 to 1600 K, in the case of the plate material, a heat treatment time satisfies the following formula (2), and in the case of bar material, a heat treatment time satisfies the following formula (3): tdif≥ (6869 / Tdif- 4.3326) × λ <2> ... (2) tdif≥ (6869 / Tdif- 4.3326) × d ... (3) where in formula (2), Tdi represents the heat treatment temperature (K), tdi represents the heat treatment time (hour), and λ represents a plate thickness (mm) of the plate material, and in formula (3 ), Tdi represents the heat treatment temperature (K), tdif represents the heat treatment time (hour), and d represents an equivalent circle diameter (mm) of the bar material.